PEN: A hierarchical document editor

Three terms in common usage in computerized text processing are text-editing, word-processing, and computer controlled typesetting. This paper deals with a fourth term, manuscript preparation, that has important intersections with the above three. A computerized manuscript preparation system is one that supports an author in the preparation of a manuscript. In what follows we deal with one such, the PEN system, directed towards the preparation of manuscripts containing significant mathematical notation.